Search Results (24)

Greater amberjack (Seriola dumerili) shows potential for Mediterranean aquaculture due to its swift growth, consumer appeal, and commercial value. However, challenges in juvenile production, such as growth dispersion and unsynchronized development, impede further expansion. This study explores the impact of rearing temperature and live feed types on early white muscle development in greater amberjack larvae. Findings reveal substantial effects of temperature and diet on larval development, highlighting that the combination of 24 °C and a copepod + rotifer co-feeding scheme resulted in the highest axial growth rate, whereas rotifer-fed larvae at 20 °C exhibited a slower pace. Incorporating both histological and gene expression analyses, the study underscores temperature’s significant influence on white muscle development. Among larvae reared at 24 °C, the two live feed types led to phenotypic variations at metamorphosis, with rotifers supporting longer larvae featuring a smaller total cross-sectional area compared to copepods. Gene expression analysis indicates heightened mylpfb and myog expression at 24 °C during early larval stages, suggesting increased hyperplasia and myoblast differentiation. This study highlights the necessity of considering both temperature and feed type in larval rearing practices for optimal muscle development, and further research exploring combined diets during rearing could offer insights to enhance amberjack aquaculture sustainability. Full article

A two-factorial experiment was conducted to evaluate the potential for improving the palatability and utilization of tuna by-product meal (TBM) as a replacement for fish meal (FM) via supplementing the diet of juvenile greater amberjack (Seriola dumerili) with powdered salmon roe liquid (PSRL). FM protein in the control diet (C) was partially replaced with TBM at levels of 25% (T25R0) and 40% (T40R0). PSRL was then added at 5% and 10% to both the T25R0 and T40R0 diets, resulting in the formulations T25R5, T25R10, T40R5, and T40R10. After a 6-week rearing period, during which groups of 30 juveniles (mean initial weight of approximately 1.7 g) were stocked in 500 L tanks, there were no significant differences in the final mean weight, weight gain, or specific growth rate among fish fed diets C, T25R0, and T25R5. However, the other experimental diets showed significantly lower values compared to the C diet (p < 0.05). PSRL supplementation did not significantly enhance either palatability or feeding rate in TBM-based diets (p > 0.05). Two-way ANOVA indicated that only FM replacement with TBM had a significant effect on the growth parameters mentioned above (p < 0.05). A significantly lower whole-body crude lipid content was observed in all test diets compared to that in the C diet, resulting in significantly lower lipid retention efficiency in all test groups except T25R5 and T25R10 (p < 0.05). These results suggest that 25% of FM protein can be replaced with TBM protein in the diet of juvenile greater amberjack, but PSRL does not effectively address the palatability issues associated with TBM-based diets. Full article

Marine heatwaves (MHWs) have recently become more frequent, intense, and prolonged, posing significant threats to marine life and fisheries. In this study, transcriptomic analysis was employed to investigate the genes and pathways in Seriola dumerili that respond to MHW-induced stress at 28 °C (T28) and 32 °C (T32), using 24 °C (T24) as the control. Transcriptome sequencing revealed that 17 differentially expressed genes (DEGs) belonging to the heat shock protein (HSP) families—HSP30, HSP40, HSP70, and HSP90—were significantly upregulated under short-lasting MHW stress in the T24-4d vs. T32-4d comparison. Additionally, genes related to oxidative stress (e.g., protein disulfide isomerase family A member 6 [pdia6]), immune responses (e.g., interferon regulatory factor 5 [irf5]), and energy metabolism (e.g., hexokinase-1 [hk1]) were also identified. Enrichment analysis of DEGs in the T24-4d vs. T32-4d group revealed that S. dumerili exhibited adaptive responses to MHWs through the upregulation of HSPs and the activation of antioxidant, energy metabolism, and immune response pathways. However, in the T24-13d vs. T32-13d group, DEGs associated with these pathways were either not significantly expressed or were downregulated. These findings indicate that S. dumerili is unable to sustain its adaptive responses under repeated, intense MHW exposure, resulting in the disorder of its antioxidant defense system, immune suppression, and metabolic dysfunction. This study provides valuable insights into the molecular responses of S. dumerili to MHWs and supports the selection for thermal resistance in this species. Full article

The greater amberjack (Seriola dumerili), a key species in marine aquaculture, relies heavily on its intestine for nutrient absorption and immune function. However, the structural and functional specialization of its intestinal segments remains poorly understood. In this study, we divided the intestine of S. dumerili into foregut, midgut, and hindgut, and conducted a multi-omics analysis integrating histological staining (H&E/AB-PAS), digestive enzyme assays, transcriptome sequencing, and 16S rRNA microbiota profiling to characterize structural, functional, molecular, and microbial differences across intestinal segments. Histological examinations revealed that brush border microvillus length, muscle layer thickness, and folding height were significantly greater in the foregut and hindgut compared to the midgut, while mucus and goblet cell density was higher in the foregut and midgut. Digestive enzyme assays showed that lipase activity peaked in the foregut, α-amylase in the midgut, and protease in the midgut and hindgut. Alkaline phosphatase (AKP) and acid phosphatase (ACP) activities were highest in the foregut and midgut. Immune-related enzyme activities (SOD (Superoxide dismutase), GSH-Px (Glutathione peroxidase), T-AOC (Total Antioxidant Capacity)) were elevated and MDA levels were lower in the midgut, indicating its role as the primary immune site. Transcriptome analysis identified segment-specific expression of nutrient transporters, such as slc6a19b (hindgut, protein), apoa1b (foregut, lipid), and slc37a4 (midgut, carbohydrate). Microbiome analysis revealed Ruminococcus dominance in the foregut (lipid digestion) and Prevotella, Bifidobacterium, and Lactobacillus enrichment in the midgut (carbohydrate metabolism and immunity). These findings highlight functional zonation in S. dumerili: the foregut specializes in lipid digestion, the midgut in carbohydrate metabolism and immunity, and the hindgut in protein digestion. This study provides foundational insights for optimizing aquaculture practices and advancing research in nutrition, immunology, and disease modeling in S. dumerili. Full article

The greater amberjack (Seriola dumerili) is an emerging marine fish that is increasingly favored in aquaculture. Currently, there are few studies on the development and regulation of greater amberjack ovaries. In this study, the ovary transcriptome profiles of greater amberjack at three different stages (stage II, III, and IV) were performed, and identified the genes and pathways that may play significant roles in the processes of follicle growth and maturation. A total of 6597, and 1061 differentially expressed genes (DEGs) were detected in FII vs. FIII, FIII vs. FIV, and FII vs. FIV stages, respectively. GO and KEGG enrichment analyses revealed that these DEG_S are primarily involved in steroid hormone biosynthesis (e.g., cyp11a1, cyp17a1, cyp19a1a, hsd3b1, esr1), lipid metabolism (e.g., plpp3, lpl, pld1, and fabp10a), and meiotic arrest and resumption (e.g., pgr, arb, ccnd2, adcy2, adcy9, myl9, calm1). Additionally, several signaling pathways involved in ovarian development have been identified, including the PI3K-Akt, Wnt, TGF-beta, GnRH, and immune-related signaling pathways. qPCR results of nine representative genes related to steroid hormone synthesis and cell growth verified the reliability of the generated RNA-seq data. This research contributes to our comprehension of the molecular processes underlying ovarian growth and maturation in marine fishes and provides a theoretical basis for the investigation of functional genes associated with oogenesis in greater amberjack. Full article

The suitability of tuna by-product meal (TBM) as a replacement for fish meal (FM) in the diet of juvenile greater amberjack Seriola dumerili was investigated for its effect on growth, mercury (Hg) levels in the fish body, phosphorus (P) load, and plasma chemistry. FM was the main protein source in the control diet (C), and it was replaced by TBM at 25%, 50%, 75%, and 100% to formulate diets TM25, TM50, TM75, and TM100, respectively. The experiment was performed in triplicate, stocking 30 juveniles (mean weight: approximately 6.7 g) in each 500 L tank. After a 42 d rearing period, there were no significant differences in growth, nutrient digestibility, or productive value between diets C and TM25. However, a quadratic polynomial regression analysis suggested that the optimal dietary level of TBM against final weight was 14.5%. A significant linear correlation was observed between Hg in the diet and fish whole body, but the level was far lower, posing health risks to humans. Owing to the lower P intake of fish fed with the TBM-based diets, their P load was significantly reduced compared to the control group. Plasma levels of total protein, total cholesterol, and albumin in the TM75 and TM100 groups were significantly lower than those in the C, TM25, and TM50 groups. These results suggest that 14.5% of FM protein can be replaced by TBM protein in the diet of juvenile greater amberjack and that a significant reduction in P load can be achieved with a TBM-based diet. Full article

Acute hypoxia is a common abiotic stress in commercial aquaculture and has significant effects on fish physiology and metabolism. Due to its large size and rapid growth, the greater amberjack (Seriola dumerili) is an economically important fish with high farming value. This species is intolerant to hypoxia, which makes it susceptible to mass mortality and hinders the progress of amberjack cultivation. Based on a comparative analysis of the liver transcriptome between acute hypoxia-tolerant (HT) and -intolerant (HS) groups, this study first explored the molecular mechanisms of acute hypoxia in greater amberjack. By simulating the acute hypoxic environment and using RNA sequencing (RNA-Seq), the differences in liver transcriptional changes between the acute hypoxia-tolerant (HT) and hypoxia-intolerant (HS) groups of greater amberjack were probed. Based on differential expression analysis, 829 differentially expressed genes (DEGs) were screened in both groups. Relative to the HS group, 374 DEGs were upregulated and 455 were downregulated in the HT group. Compared with the HS group, genes such as slc2a5 and prkaa2 related to promoting sugar transport and inhibiting lipid syntheses were upregulated, while genes that inhibit gluconeogenesis and promote lipid syntheses, such as pgp and aacs, were downregulated. The expression of odc1 was significantly and relatively downregulated in the HT group, which would lead to the inhibition of intracellular antioxidant activity and decreased scavenging of ROS. The NF-kB pathway was also promoted to some extent in individuals in the HT group relative to the HS group to resist apoptosis. In addition, the relative downregulation of apoptosis and autophagy-related genes, such as endog, hm13, and casp6, was also detected in the HT group. The present findings first reported the regulation mechanism by which liver tissue coped with the acute hypoxia stress in greater amberjack, which will provide important technical support for preventing acute hypoxia-induced death in advance and reducing economic losses. Full article

Greater amberjack (Seriola dumerili) is a new species in marine aquaculture with high mortalities at the larval stages. The microbiota of amberjack larvae was analyzed using 16S rDNA sequencing in two groups, one added copepod nauplii (Acartia tonsa) in the diet, and one without copepods (control). In addition, antagonistic bacteria were isolated from amberjack larvae and live food cultures. Proteobacteria was the most abundant phylum followed by Bacteroidota in amberjack larvae. The composition and diversity of the microbiota were influenced by age, but not by diet. Microbial community richness and diversity significantly increased over time. Rhodobacteraceae was the most dominant family followed by Vibrionaceae, which showed the highest relative abundance in larvae from the control group 31 days after hatching. Alcaligenes and Thalassobius genera exhibited a significantly higher relative abundance in the copepod group. Sixty-two antagonistic bacterial strains were isolated and screened for their ability to inhibit four fish pathogens (Aeromonas veronii, Vibrio harveyi, V. anguillarum, V. alginolyticus) using a double-layer test. Phaeobacter gallaeciensis, Phaeobacter sp., Ruegeria sp., and Rhodobacter sp. isolated from larvae and Artemia sp. inhibited the fish pathogens. These antagonistic bacteria could be used as host-derived probiotics to improve the growth and survival of the greater amberjack larvae. Full article

Metamorphosis entails hormonally regulated morphological and physiological changes requiring high energy levels. Probiotics as feed supplements generate ameliorative effects on host nutrient digestion and absorption. Thereby, the aim of the present research was to investigate the impact of the probiotic Phaeobacter inhibens as a water additive on cellular signaling pathways in the metamorphosis of greater amberjack (Seriola dumerili). Activation of insulin-like growth factor type 1 receptor (IGF-1R), protein kinase B (Akt), mitogen-activated protein kinases (MAPKs) and AMP-activated protein kinase (AMPK), induction of heat shock proteins (Hsps), and programmed cell death were assessed through SDS-Page/immunoblot analysis, while energy metabolism was determined through enzymatic activities. According to the results, greater amberjack reared in P. inhibens-enriched water entered the metamorphic phase with greater body length, while protein synthesis was triggered to facilitate the hypertrophic growth as indicated by IGF-1/Akt activation and AMPK inhibition. Contrarily, MAPKs levels were reduced, whereas variations in Hsps response were evident in the probiotic treatment. Apoptosis and autophagy were mobilized potentially for the structural remodeling processes. Furthermore, the elevated enzymatic activities of intermediary metabolism highlighted the excess energy demands of metamorphosis. Collectively, the present findings demonstrate that P. inhibens may reinforce nutrient utilization, thus leading greater amberjack to an advanced growth and developmental state. Full article

The present study was conducted to investigate the effects of dietary fish oil replacement with a mixture of vegetable oils and probiotic supplementation on plasma biochemical parameters, oxidative stress, and antioxidant ability of Seriola dumerili. Specimens with an initial weight of 175 g were used. Four feeds were formulated with 0% (FO-100), 75% (FO-25), and 100% (FO-0 and FO-0+ with the addition of Lactobacillus probiotics) substitution of fish oil with a mixture of linseed, sunflower, and palm oils. After 109 days, no significant differences were observed in the activity of antioxidant enzymes in the liver, foregut, and hindgut, only glucose-6-phosphate dehydrogenase activity in the liver was higher in the fish fed the FO-100 diet than in those fed the FO-0 diet. No significant differences were observed in the total, reduced, and oxidized glutathione and the oxidative stress index in the liver. In addition, lipid peroxidation in the liver and red muscle values were higher in the fish fed the FO-100 diet than in the fish fed the FO-0+ diet, however, the foregut of the fish fed the FO-100 diet presented lower values than that of the fish fed the FO replacement diet, with and without probiotics. There were significant differences in cholesterol levels in the FO-100 group; they were significantly higher than those observed with the fish diets without fish oil. To sum up, fish oil can be replaced by up to 25% with vegetable oils in diets for Seriola dumerili juveniles, but total fish oil substitution is not feasible because it causes poor survival. The inclusion of probiotics in the FO-0+ diet had no effects on the parameters measured. Full article

This study provides the first socio-ecological overview of the Seriola dumerili fishery occurring in the Balearic Islands. This pelagic top-predator is among the five most valued fish resources of the Balearic community. Despite its ecological importance and potential vulnerability to aggregation fishing, few studies address the ecology of this large Carangidae species. Shining a light on its ecology is vital to ensure adequate species conservation and the sustainable and effective management of the fishery. Historical catches from 1950–1999, alongside detailed landing data for the last 21 years, were analysed to identify potential patterns in ecological and socio-economic factors. Significant inter-annual variability among the years was found in historical catches of greater amberjack, while catches and mean prices of the different size categories revealed significant results between seasons and months, respectively. Additionally, the purse seine fleet accounted for the highest percentage of S. dumerili catches. CPUE did not appear to change greatly between months and years after the annual 8-month fishing ban imposed in 2011 and therefore a re-evaluation of the closure was intended. Overall, this study suggests seasonality influences the S. dumerili fishery in the Balearic Islands, within which ecological influences show a higher regulating power than socio-economic factors. Full article

The greater amberjack (Seriola dumerili) is a gonochoristic fish with no sexual dimorphism in appearance, making sex identification difficult. Piwi-interacting RNAs (piRNAs) function in transposon silencing and gametogenesis and are involved in various physiological processes, including sex development and differentiation. Exosomal piRNAs can be indicators for the determination of sex and physiological status. In this study, four piRNAs were differentially expressed in both serum exosomes and gonads between male and female greater amberjack. Three piRNAs (piR-dre-32793, piR-dre-5797, and piR-dre-73318) were significantly up-regulated and piR-dre-332 was significantly down-regulated in serum exosomes and gonads of male fish, compared to female fish, consistent with the serum exosomal results. According to the relative expression of four marker piRNAs derived from the serum exosomes of greater amberjack, the highest relative expression of piR-dre-32793, piR-dre-5797, and piR-dre-73318 in seven female fish and that of piR-dre-332 in seven male fish can be used as the standard for sex determination. The method of sex identification can ascertain the sex of greater amberjack by blood collection from the living body, without sacrificing fish. The four piRNAs did not show sex-inclined expression in the hypothalamus, pituitary, heart, liver, intestine, and muscle tissue. A piRNA–target interaction network involving 32 piRNA-mRNA pairs was generated. Sex-related target genes were enriched in sex-related pathways, including oocyte meiosis, transforming growth factor-beta signaling pathway, progesterone-mediated oocyte maturation, and gonadotropin releasing hormone signaling pathway. These results provide a basis for sex determination in greater amberjack and improve our understanding of the mechanisms underlying sex development and differentiation in the species. Full article

In this study, we investigated the effect of dietary curcumin on non-specific immune responses and antioxidative ability in Seriola dumerili under ammonia stress and post-recovery. Three diets were prepared to contain 0, 75, and 150 mg/kg of curcumin. A total of 225 greater amberjack (initial weight: 100.90 ± 0.03 g) were distributed into nine cylindrical tanks, constituting an experimental design with three treatments and three replicates. After 56 days of feeding, plasma, intestinal, and hepatic enzyme activities were evaluated. Then, an acute ammonia challenge experiment was conducted. Ten fish per tank were subjected to acute ammonia stress (total ammonia-N: 1000 mg/L) for eight minutes followed by six minutes of recovery. The results indicated that dietary curcumin significantly promoted intestinal and hepatic alkaline phosphatase (ALP) and acid phosphatase (ACP) levels as well as hepatic antioxidative enzymes such as superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reduced glutathione (GSH), and glutathione peroxidase (GSH-Px) of greater amberjack. In addition, curcumin addition improved the activities of antioxidant enzymes, such as SOD, T-AOC, GSH, GSH-Px, and catalase (CAT), and reduced malondialdehyde (MDA) content in liver, spleen, head kidney, and brain tissues after post-recovery. The indexes related to immunity and antioxidant enzymes in the liver, gill, and spleen rose again to some extent, but they showed the worst recovery ability in the head kidney and brain tissue samples. These results indicate that dietary curcumin supplementation could increase non-specific immune responses, antioxidant ability, and enhance resistance to high ammonia stress in juvenile S. dumerili. Full article

This study was conducted to determine whether curcumin has a positive effect in greater amberjack (Seriola dumerili), especially the ammonia nitrogen stress tolerance ability. The results showed that the stress recovery process of digestive enzymes amylase and trypsin, as well as absorptive enzymes Na⁺/K⁺-ATPase, γ-GT and CK, was accelerated. Lysozyme activity increased in the fish fortified with both curcumin diets. Aspartate aminotransferase activity restriction was activated at a low curcumin level. However, alanine aminotransferase activity restriction happened only at 0.02% dietary curcumin. Facilitation of lipid metabolism by curcumin was very clear, as triglyceride and total cholesterol content was basically maintained at the original level or even showed a slight decrease after recovery. HSP70 and HSP90 genes were not evidently stimulated to express in liver, kidney and spleen tissues. In addition, curcumin showed its inhibition capacity on IL1β and IFN-γ and a promoting effect on TGF-β1. The expression of NF-κB1 decreased in a higher degree in fish fed with 0.02% dietary curcumin, while 0.01% dietary curcumin accelerated the recovery pace of C3 and lgT after stress. This study showed that dietary curcumin supplementation can enhance ammonia nitrogen stress tolerance in greater amberjack, and its application prospect can be confirmed. Full article

This study investigated the effects of added eugenol on water quality and the metabolism and antioxidant capacity of the liver and gills of the greater amberjack (Seriola dumerili) during simulated transport. The juvenile fish (10.34 ± 1.33 g) were transported in sealed plastic bags containing different eugenol concentrations at a density of 24.79 kg/m³ for 8 h. The different eugenol concentrations were divided into five groups: 0 μL/mL (control group), 0.0125 μL/mL, 0.025 μL/mL, 0.0375 μL/mL, and 0.05 μL/mL, with three replicates of each. The results showed that 0.05 μL/mL of eugenol could significantly increase dissolved oxygen, but 0.025 μL/mL–0.0375 μL/mL resulted in a significant decrease in dissolved oxygen and significant increases in NH₄⁺-N and NO₂⁻-N. It was found that 0.05 μL/mL of eugenol caused significant up-regulation of the relative expression of CPT-1 in the liver, significant down-regulation of the relative expression of FAS and PK in the liver and gills, a significant increase in glycogen concentration, and a significant decrease in glucose concentration. This suggests that 0.05 μL/mL of eugenol could reduce the metabolic capacity of fish. In addition, 0.05 μL/mL of eugenol caused significant up-regulation of the relative expression of CAT and a significant decrease of MDA concentration in the liver. Meanwhile, the gills showed significant up-regulation of CAT relative expression, significant down-regulation of Keap1 relative expression, and a significant increase in GSH activity, resulting in a significant increase in MDA concentration when the concentration of eugenol reached or exceeded 0.025 μL/mL. This suggests that 0.05 μL/mL eugenol could improve the antioxidant capacity of fish and lipid peroxidation levels in the gills. In conclusion, the addition of 0.05 μL/mL eugenol could improve water quality, and the metabolic and antioxidant capacities of liver and gills, but it could also increase lipid peroxidation levels in the gills under transport conditions. Full article